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<h1><a href="https://archiveofourown.org/works/28947543">First</a> by <a class='authorlink' href='https://archiveofourown.org/users/FullOfBoredom/pseuds/FullOfBoredom'>FullOfBoredom</a></h1>

<table class="full">

<tr><td><b>Category:</b></td><td>Undertale (Video Game)</td></tr>

<tr><td><b>Genre:</b></td><td>M/M, Nightkiller - Freeform, killermare - Freeform</td></tr>

<tr><td><b>Language:</b></td><td>English</td></tr>

<tr><td><b>Status:</b></td><td>Completed</td></tr>

<tr><td><b>Published:</b></td><td>2021-01-24</td></tr>

<tr><td><b>Updated:</b></td><td>2021-01-24</td></tr>

<tr><td><b>Packaged:</b></td><td>2021-05-13 04:49:10</td></tr>

<tr><td><b>Rating:</b></td><td>Explicit</td></tr>

<tr><td><b>Warnings:</b></td><td>No Archive Warnings Apply</td></tr>

<tr><td><b>Chapters:</b></td><td>1</td></tr>

<tr><td><b>Words:</b></td><td>3,108</td></tr>

<tr><td><b>Publisher:</b></td><td>archiveofourown.org</td></tr>

<tr><td><b>Story URL:</b></td><td>https://archiveofourown.org/works/28947543</td></tr>

<tr><td><b>Author URL:</b></td><td>https://archiveofourown.org/users/FullOfBoredom/pseuds/FullOfBoredom</td></tr>

<tr><td><b>Summary:</b></td><td><div class="userstuff">
              <p>Killer takes a first.</p>
            </div></td></tr>

<tr><td><b>Relationships:</b></td><td>Sans/Sans (Undertale)</td></tr>

<tr><td><b>Comments:</b></td><td>13</td></tr>

<tr><td><b>Kudos:</b></td><td>81</td></tr>

</table>

<a name="section0001"><h2>First</h2></a>
<div class="story"><div class="userstuff module">
    
    <p>Killer entered into the kitchen with a tense back, casually perusing the fridge with a wince. He’d taken a hard hit on the side during the last fight with the Stars. Probably cracked something, but nothing was falling off so he didn’t bother too much with it. His determination would hold him together.</p>
<p>He grabbed the carton of milk and took a swig straight from the container.</p>
<p>“Other people use that you know.” </p>
<p>“Too bad for them.” Killer turned around to grin at Nightmare. He’d recently gotten into his Boss’s VERY good graces and no broken bones were going to keep him out of it. “Well if it isn’t small, dark, and Lovecraftian.” That got a chuckle, a rare thing to hear from Nightmare. It made his target soul ache something awful, hearing that cute sound and not being able to do anything with it, not nearly close enough to Nightmare to capitalize on the opportunity. </p>
<p>“As good with words as with a knife, hmmm?” Nightmare stood in his space, touching along his arm unconsciously. Killer tried to keep his mouth in check.</p>
<p>“I’m also pretty good with my hands.” God damn idiot brain, hitting on his fucking god level boss. There’s fucking with people and there’s shooting out of your league. He just smiled through it. “Whatcha need Boss?”</p>
<p>“I’m moving a wing of the library and needed an extra pair of hands.” </p>
<p>“And you knew how talented mine were, so you came right to me?” Killer slid the milk back into the refrigerator. He leaned back on his left side to keep from agitating the right, elbows on the counter, a picture of relaxation. </p>
<p>“Something like that.” Nightmare laughed again. Killer held in the pleased sigh, standing up, crossing his arms behind his head very delicately.</p>
<p>“I’m all yours Boss. Lead the way.”</p>
<p>They wandered down the hall directly towards the library, Killer keeping step just behind Nightmare, letting him stare all he wanted without being caught. Those strong thick tentacles swayed around his back, framing his ass for Killer to appreciate along the lengthy hallways. He rarely went over this way unless Night summoned him here.</p>
<p>Nightmare already cleared small sections away, stacks of meticulously organized books littering the floor. He gestured to a pile.</p>
<p>“Start here and work clockwise. I’ve laid it out to make it easy enough for you to do without me babysitting your progress.” </p>
<p>So began replacing them on the shelves. Killer hid the winces of pain from stooping and bending fairly well, silently moving until he hit a tiny snag. He reached up to place one on a tall shelf when he flinched into the wall.</p>
<p>His body hit the shelves and dislodged an avalanche onto his head. He almost moved away before one smashed into his cracked ribs.</p>
<p>“Son of a fucking bitch!</p>
<p>"Killer!” Nightmare raced over to unbury him. The tentacles made quick work of them, stacking haphazardly off of Killer’s winded form. His hands were on Killer’s forehead in an instant, checking for cracks, diligently looking over him after hearing the cry of pain. Killer groaned angrily when he was cleared off.</p>
<p>“Fucking Blue and his fucking blue attacks. Ugh.” Killer couldn’t sit up, pain still blossoming fresh in his chest. Night paused in looking him over.</p>
<p>“Were you wounded on the last mission?” His single eye penetrated his two, pinning him under it until he relented, grimacing with a gesture to his ribs he’d been carefully avoiding.</p>
<p>“Yeah. Stars got a good hit in on me. Was fine until the book hit it though.”</p>
<p>“Clearly not, considering you lost your usually impeccable balance!” Nightmare’s tentacles wrapped Killer up to get him standing without making him bend the wounded area. “Come with me. Healing magic is easiest when accompanied by intent, wrapping it will make it easier.” He grumbled and took off towards his room, Killer hobbling after to keep up. </p>
<p>Walking into Night’s room changed the mood. He suddenly felt out of place, surrounded by luxurious purples tones and dark wooden furniture. Night had gestured to the bed before wandering into his private bathroom.</p>
<p>His bed was comfortable. Killer’s nerves ruined any enjoyment of getting into Nightmare’s room, jittery from the moment he was directed to sit on the plush comforters. Nightmare returned with a roll of bandages and an unimpressed look.</p>
<p>“I thought you were smart enough to know how to care for yourself.” He moved in front of him. “Take off your jacket and t-shirt.”</p>
<p>Thankfully Night was too focused on unraveling the bandages and gathering antiseptic to see Killer’s face go red, suddenly very aware that he was in his boss’s room, said boss’s hands about to be on him after a request to undress. He pulled them off smooth and casual, but his grin practically cracked at the edges. </p>
<p>“What the hell?”</p>
<p>Night’s hands hovered over the cracked ribs, flinching back at the small break that Killer had dislodged from its setting.</p>
<p>“Yeah, it’s not great.”</p>
<p>“Killer!” Night growled at him. “Why didn’t you seek treatment before THIS?!” He gestured to the crumbled ends of the break from grinding against each other. “This is entirely fucking curable! It’s ridiculous you didn’t, at the very least, wrap this!” The growl travelled up his body, baring his teeth at him, tentacles cracking like whips at his back. Killer didn’t move, but his voice took on a nervous edge.</p>
<p>“I’m a dead man walking boss. I’ll just keep going forward until I can’t anymore.” Healing magic was taxing. All of them were terrible at it besides Nightmare, who never offered, only taking over when he was clearly needed. They never want to bother him to ask for it.</p>
<p>“I could’ve fixed this sooner.” Nightmare pinched the bone into place with a click. Killer gasped in pain. He wrapped it tightly, uncaring about Killer’s harsh pants while doing so.</p>
<p>“We only take it when you offer. None of us wanna annoy you.” Fuck, he was so falling out of Night’s good graces for this. After he worked so hard, some dumb break was gunna take him back to zero. He fisted the plush comforter. “Your time is important.”</p>
<p>“To whom, when you dust from accumulating injuries that I can’t see?” </p>
<p>“The multiverse I guess.”</p>
<p>“The multiverse doesn’t give a shit about me or my time. This is all I have.” Nightmare pinched his nasal crest after finishing. “You serve me, but I cannot do this alone. Your lives are valuable to me. I thought you, especially, would know this Killer.“</p>
<p>"Why do ya say that?”</p>
<p>“Because of how important you are to me.” Nightmare’s hands grew warm with gathering magic, mending now that everything would heal correctly. “All of you are valuable, like the supporting beams holding the castle aloft, but you are more integral. You are the center pillar. As my right hand, as long as you stand, I have faith in my ability to recover. I believed you to be my most valuable asset, but if you’re going to just let yourself turn to dust, then I’ll-”</p>
<p>“No!” Killer’s soul snapped into a heart shape, eyelights flickering in time to meet Night’s inquisitive gaze. “I’m not dusting on you just like that.” He grabbed Night’s warm hands away, taking them up in front of his startled cyan face.</p>
<p>“K-Killer?” He brought them up and kissed the phalanges as one would do to their king.</p>
<p>“If you’ll continue as long as I am by your side, then I’ll remain with you until I die.” Killer’s sockets went half-lidded, struck by the emotion his inverted soul let in, his silly crush amplified ten-fold by Nightmare’s faith in him. He’d never seen his boss look so confused, eye wide and frantically searching Killer’s. “What’s wrong boss?” </p>
<p>“You-I’m…what’s-why all-”Killer’s hands had long since gained a mind of their own. He slid wordlessy off the bed into Night’s space, silencing him with a casual touch on the cheek, fondly caressing the bright greenish glow. </p>
<p>“Shouldn’t have told me I meant so much to ya cuz I’m gunna take that to heart.” Then he swooped down to kiss him.</p>
<p>Killer pressed their teeth together firmly, tilting their heads to line up for deepening the kiss. He relaxed into it, holding Nightmare close while getting a taste, slowly touching and teasing Night’s tongue with playful flicks. He could feel the very hesitant kiss back before they parted for air.</p>
<p>"Feeling shy Nightmare? Don’t worry. I’m bold enough for the both of us." </p>
<p>Killer laughed into the next one, leaning into it to force Night’s response, groaning at the feel of the shy tongue in his own mouth. He could feel his small partner shaking in his arms when they broke apart.</p>
<p>"Killer…” It must’ve been awhile since Nightmare got with anyone to sound so needy. </p>
<p>“I’m here. Wanna have some fun Nightmare?” He whispered it into Night’s ear, smiling at the trembling he could still feel against his ribs, lost in the heady feeling. Night devolved to breathy pants, which Killer dove into before he felt tentacles lay solidly against his chest to push him back.</p>
<p>“Killer, wait, I can’t-I’m not prepared for this.” Night’s flushed face told a different story, but he didn’t fancy being killed.</p>
<p>“I’ve got lots of patience. I’ll just make you feel good until you are.” Killer’s mouth slid down to Night’s neck, sucking on the bone to the high pitched whines, sending all his thoughts south, ecto eager to form at the slightest provocation. His haze broke under the Night’s firm push out of his space. </p>
<p>“Killer, <em><b>stop</b></em>." </p>
<p>His back connected with the bed, wincing from his still (though much less so) wounded bones. The rejection stung worse.</p>
<p>"Sorry boss.” That HURT, knowing he’d fucked up pretty royally. God, he’d forced himself on Nightmare right after he’d been given a shred of attention. He was such a fucking idiot. “I’ll keep my hands to myself.” His eyelights poofed decisively. He almost couldn’t bear to look at him, but he needed to see Nightmare’s face at least once.</p>
<p>Night hadn’t stopped shaking. His tentacles attempted to hide him from view, face fully blushing, head still tilted away from the fresh mark Killer had left, noises leaking unfiltered from his trembling body. </p>
<p>“S-s-sorry. I-I c-can’t handle it-t. Too much.” Killer grabbed his shirt and hoodie from where it lay beside him.</p>
<p>“I’ll leave you be. Maybe annoy Horror or something, I don’t know.” Anything to not be here. Playing it off would make it easier to take, even if it meant no second chances with Night. He slid his clothes back on. “Come find me when you got the next mission lined up.”</p>
<p>A tentacle wrapped around his ankle before he took the first step.</p>
<p>“Why are you leaving?” His voice was airy, light, breathless.</p>
<p>“I’m a dick, but not that much of one. I went too far, I’ll give ya some space for a day.” He shrugged, a drop of hate splashing on the floor. He’d describe his emotions as ‘in shambles.’</p>
<p>“I don’t want space. I just need a minute.”</p>
<p>“I don’t know Boss. Shouldn’t rush that kind of thing.” He could stomach taking advantage of people outside of this castle, but betraying the ones inside it, those who guarded his back and knew where he slept (and cared about but he’d never tell them that), it turned his mood sour. It ate at the pit of his stomach and it’d eat through him entirely if he didn’t get the fuck outta dodge.</p>
<p>“What thing?”</p>
<p>“Being assaulted, harassed, whatever you wanna call it. And being the person who forced themselves upon ya, don’t think I should be here.” He tugged at his ankle again, but Night hadn’t relented.</p>
<p>“Killer, I didn’t stop you because I didn’t want it.” He avoided Killer’s eye roll.</p>
<p>“Uh-huh.” Killer really didn’t want to resort to cutting off the tentacle. It wouldn’t hurt him, but it’d suck and prove he was an asshole, so he pulled harder. “Say I believed you. Then why?”</p>
<p>“Killer, I…” Nightmare looked like he wanted the carpet to swallow him. “I’ve never kissed anyone.”</p>
<p>“…<em><b>What</b></em>?” He stopped struggling against his restraint. “There’s no way. You’re telling me, five hundred years of existing, and you hadn’t had your first kiss?”</p>
<p>“Yes.” And Killer commited a cardinal sin without thinking.</p>
<p>“But Dream definit-” Is fucking Ink or Blue or Cross or all of them, he wanted to say, but Night was quicker.</p>
<p>“I am <em>aware.</em>” Nightmare’s glare was potent, but Killer’s confusion was denser. “But he is lovable, unlike me.”</p>
<p>“You’re lovable.” It slipped out in-between all the mental gymnastics. He wasn’t sure he wasn’t being fucked with still. “So you haven't…” How to phrase this delicately, he wondered. “…slept with anyone?”</p>
<p>“Killer, I haven’t kissed anyone. Why the fuck would I have slept with someone?”</p>
<p>“You gotta know how unbelievable this is.” Talking wouldn’t reassure him, so Killer leaned down into Night’s space again, stopping just shy of his teeth. “You’re telling me that someone as fuckable as you’s been ignored all this time?” Nightmare’s single eye widened with the flush. Killer smoothed out his tone, dropping it low to hold him at the edge of his words. “Nice juicy peach you are, no one’s tried to pluck you up? I can barely look without salivatin’.” He lapped at his teeth, careful to keep his hands in safe places. He wanted to see how inexperienced Night really was without ruining his chances forever.</p>
<p>Nightmare’s tentacles laid limp behind him, all the tremors coming from his real form, whose hands had raised to snatch at the shoulders of his hoodie, gripping tightly when he caved under the languid licks at his mouth by letting Killer in.</p>
<p>Patience led this one, Killer carefully taking over every inch of Night’s mouth. The slower pace served to work up his partner faster. Nightmare’s calmness abated, tentacles waking up to come and clutch at Killer’s form, Night crawling onto him, transforming the kiss into a frenzy of desire that Killer surrendered to, as long as Night was leading the way. The tentacles touched plenty of hot spots, but he kept his own hands on innocent ground. Night’s confidence could crumble under too much of a good thing.</p>
<p>“Take a breath, Nightlight.” Night shivered against him after breaking apart, so much sensation his body was unaccustomed to. “I gotcha.” Killer rubbed soothing circles into his back.</p>
<p>“I can see how that could escalate.” Nightmare finally got out. It made him laugh. </p>
<p>“Yeah. It’s pretty easy to get carried away.” He kissed the top of his skull before laughing again. “You give handsy a whole new meaning though.”</p>
<p>“Sorry.” The sweet little monster in his arms barely resembled his boss, hiding his face by burrowing into Killer’s chest. </p>
<p>“Don’t be. It’s pretty hot.” His lewd grin made Night blush again.</p>
<p>“I would’ve thought my corruption would be the ugliest and most disgusting part of me.” He punctuated it with said appendages undulating behind him.</p>
<p>“Boss, I just kissed the fuck outta you and I’ve never known you without it. Trust me, not a deterrent.” Killer stroked down one to make Night’s spine curl. “If you learn how to use ‘em right, they’re pretty useful in the bedroom.”</p>
<p>“Don’t call me Boss when we’re like this.” Night whispered softly. His face caught between a glare and something soft, he was starting to come back to his senses.</p>
<p>“That might be too much power Nightlight.” He grinned at the tiny glare. “How was your first kiss then?”</p>
<p>“Nice.” Nightmare sighed as he sat up, unfurling all the aching limbs. The usual persona rebuilt itself. But now, Killer knew how easy the composure was to break. “I’d like to repeat it sometime.”</p>
<p>“I’m all yours.” He’d never get sick of that face if Night was willing to let him see it. They rose together from the floor, Night reestablishing the space between them.</p>
<p>“I’ll have to talk to the others about not bringing injuries to me. Time spent on them is not time wasted.” He straightened his sweater, presentable before opening the door. Killer choked the urge down to mess it up again. “The idea that you would’ve rather lost a rib than speak to me is absurd.”</p>
<p>“Yeah.” They better not take his catch. Fuck them.</p>
<p>“I’m not going to kiss them Killer. The sour look is atrocious on you.” Night’s brow raised. Caught red handed. Killer laughed.</p>
<p>“Can you blame me? I know the kind of filthy degenerates who live here; I’m one of them. I don’t want 'em to take a bite outta you.” Subconsciously, he shook his sleeves to feel the weight of his multiple blades.</p>
<p>“You act as though there are many vying for my affection. People used to throw rocks at me for walking by their homes, and now they try to kill me. I’m not surrounded by suitors.” He said this while walking down the hall towards the still upturned library. His strides were confident, power inherent is his manner, carried with a royal grace that Killer could only ape with minimal success. The only reason he wasn’t swamped with competition was everyone had been too chickenshit to make a move. </p>
<p>“Ya also thought I wasn’t interested and nothing has ever been less fucking true.” He pushed his luck a little further, stepping in front of Nightmare to kiss him quickly. The chaste thing was almost too much considering the shakes. “I’ll just keep doing it if ya don’t say anything.”</p>
<p>“We need to reassemble the library.” He huffed through, walking by with weak knees, Killer trailing just behind. “This wasn’t an invitation to touch me at all times.”</p>
<p>“Only some of the time then?” </p>
<p>“Shut up.” He humored the request once inside Night’s treasured library. </p>
<p>Back to quietly organizing, clockwise, his talented hands flipped them onto shelves with ease now that he wasn’t hindered by aches. It was quick and effortless like it should have been the first time. He’d begun humming by the time he placed the last one, not expecting the hand on his shoulder but welcoming it as he had earlier the same day. Night silently pressed something into his palm.</p>
<p>“I trust I don’t need to explain.” Killer’s fingers closed over the silver key, smiling and spinning it on his pointer while leaving the now neat library. Guess his league was a lot wider than he thought. It wasn’t an invitation to his bed, but the invitation to his heart was just as good.</p>
<p>“Gotcha loud and clear boss. See ya soon.” </p>
  </div><div class="fff_chapter_notes fff_foot_notes"><b>Author's Note:</b><blockquote class="userstuff"><p>I decided I needed more happy Killermare, even though I’ve literally written a ton of it. I should write literally anybody else next…&gt;_&gt;</p></blockquote></div></div>
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